The present invention relates to the removal of metal, nitrogen and sulfur contaminants from organic compositions. More specifically, the present invention relates to the removal of metal, nitrogen, and sulfur contaminants from organic compositions by the use of methylating agents.
It is known that many organic compositions, particularly hydrocarbons such as crude oil, contain at least small amounts of a contaminating metals, sulfur and nitrogen which are detrimental, particularly in the processing of such materials to produce commercially valuable products. In the recent past, light crude oils have been available in sufficient quantities to permit their use almost exclusively for the production of commercially valuable products such as gasoline, fuel oils, and feedstocks for petrochemical production. Such oils contain very small amounts of metallic contaminants and nitrogen. Therefore, the only contaminant of any significance was sulfur. However, the sulfur is present in such oils in relatively small amounts and in a form which can be readily removed by techniques such as hydrogenation. The current shortage of light, sweet crude oils has substantially increased the necessity of utilizing heavier crude oils as well as oils produced from coal and lignite, tar sands, shale and the like and will undoubtedly increase rapidly in the future. By contrast to light crude oils, such heavy oils and synthetic oils contain substantially larger amounts of sulfur and more complex in difficult to remove forms, substantial amounts of nitrogen compounds also in a difficult to remove form as well as significant amounts of metals, such as vanadium and nickel. The sulfur and nitrogen not only form acidic compounds which are detrimental in further processing but produce significant amounts of air pollutants when the products are burned as fuels. The presence of metals also makes further processing difficult since the metals generally act as poisons for catalysts employed in processes such as catalytic cracking, hydrogenation, hydrodesulfurization, etc. At the present time, the most prevalent technique for the removal of sulfur and nitrogen is hydrogenation. However, the removal of sulfur requires substantially larger amounts of hydrogen and more severe conditions than previously utilized and the removal of nitrogen requires still higher volumes of hydrogen and more severe conditions. The necessity of utilizing substantial amounts of hydrogen also creates a problem not heretofore encountered. In most refinery operations, a catalytic reforming unit exists which has a net production of hydrogen. In the past, the hydrogen produced by a catalytic reforming unit has been sufficient to supply all of the hydrogen needs of the refinery. However, where the heavier feed materials, which are highly contaminated, are to be processed this is no longer the case and additional hydrogen must be produed by other means such as methane reforming, etc. In the past, there has been no particularly effective and economical means of removing metallic contaminants from the crude oils, etc. Instead, the problems created by the presence of such metals have been essentially neutralized during catalytic treating operations such as hydrocracking by techniques such as metal passivation. In any event, the seriousness of the above mentioned problems requries that some technique be available for the removal of such contaminants and the removal of even small amounts prior to or during processing would be highly advantageous.